People who go online a lot experience significant physiological changes — including increased heart rate and blood pressure — as well as higher anxiety, when they finish using the internet, according to a new study published in the journal, PLOS ONE; this study is the first controlled experiment to definitely link physiological changes and internet exposure, the researchers say, though others have shown a link between internet use and depression and loneliness. These symptoms mimic the withdrawal symptoms experienced by “many sedative drugs, such as alcohol, cannabis, and heroin,” the report notes.

The researchers asked people ages 18-33 how much time they spent on the Internet — on average, 5 hours a day — on all types of sites from social networking (92% use these) to shopping/banking (90%) to news (69%%) to dating and sexual sites (56%). They then asked them if they thought they used the internet too much. Four in 10 said they did, with their internet usage averaging about 7-9 hours a day.

Hours spent online each day

Percentage who spend this much time online

Less than 3 hours a day

38%

3-6 hours

39%

6-9 hours

9%

More than 9 hours

14%

And this group did not fare well when they had to log off. Participants saw a 3-4% average increase in heart rate and blood pressure — and in some cases double that figure, as well as higher anxiety. “Although this increase is not enough to be life-threatening, such changes can be associated with feelings of anxiety,” the researchers note. And “a problem with experiencing physiological changes like increased heart rate is that they can be misinterpreted as something more physically threatening,” says co-author Lisa Osborne.

What may be happening here is that internet use is physically addicting like a drug experts say. Indeed, it “can often mirror the characteristics of drug or alcohol addiction: People who are constantly online can experience ‘withdrawal’ symptoms when they’re forced to unplug,” explains Jamison Monroe, the founder & CEO of Newport Academy, a mental health & drug rehabilitation center. “When they’re able to get back online and check social media, they experience a ‘high’—a noticeable mood change and a restored sense of ease.

Monroe notes that he is seeing “seeing a dramatic rise in internet addiction, as accessibility and prevalence increase.” The cost to treat such an addiction is staggering: Roughly $5,000 – $50,000, depending on the level of care needed (inpatient vs. outpatient) and the amount your insurance will cover.